Conversion of hydrocarbon oils



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CONVERSION OF HYDROGARBON OILS Filed May 29, 1955 WV mmm. ZMDZOU April 19, 1938.

INVENTOR CHARLES H. ANGELL.

Patented Apr. 19, 1938 UNITED STATES PATENT OFFICE CONVERSIONA OF HYDROCARBON OILS Application May 29, 1935, Serial No. 24,088

2 Claims.

This invention refers to an improved process for the selective cracking of relatively low boiling and high boiling hydrocarbon oils accompanied by the reduction of the residual liquid conversion Yproducts of the process, as Well as any corresponding high boiling fractions of the charging stock, to substantially dry coke within the same system.

In one embodiment, the invention comprises subjecting an oil, comprising intermediate liquid conversion products recovered from Within the process, to conversion conditions of cracking temperature and substantial superatmospheric pressure in a heating coil, introducing the hot conversion products into a separating chamber wherein quick separation of vaporous and liquid conversion products is accomplished Without substantial further cracking of either, withdrawing the vaporous conversion products from said separating chamber and subjecting the samey to continued cracking in a separate heating coil, separately 4removing liquid conversion products from said separating chamber and introducing the same into a coking chamber, introducing the heated products from said separate heating coil into the ycoking chamber for the purpose of assisting reduction of the heavy components of the liquid hydrocarbons supplied to this zone to coke, Withdrawing vaporous products from the coking chamber and introducing the same into a separate vaporizing and separating chamber, supplying hydrocarbon oil charging stock to the process to said separate vaporizing and separating chamber, wherein it is subjected to vaporization by contact with the vapors from the coking chamber, With- .drawing relatively highl boiling liquids which remain unvaporized and/or are condensed in the vaporizing and separating chamber therefrom and supplying the same to said coking chamber, whereinl they are subjected to further Vaporization and their non-vaporous components reduced to coke, subjecting vaporous products: from said vaporizing and separating chamber to fractionation whereby their components: boiling above the range of the desired nal light distillate product of the process are condensed as reflux condensate, returning reflux condensate to the rst-mentioned heating coil for further cracking, subjecting fractionated vapors of the desired end boiling point to condensation, and recovering the resulting distillate.

As a modication of the specific embodiment of the invention above outlined, the liquid conversion products separated from the vaporous conversion products in the first-mentioned separat- V. ing chamber may, When desired, be supplied, all or (Cl. ISG- 49) in part, to the second vaporizing and separating chamber instead of directly to the coking cham,- ber. This latter method of operation Will ordinarily be preferable to that abovedescribed when the first separating chamber is operated at a relatively high superatmospheric pressure and substantially reduced pressure is employed in the second vaporizing and separating chamber, since the liquid conversion products separated at relatively high pressure will ordinarily contain some relatively low boiling oils Which may be separated from its higher boiling components by the further vaporization at substantially reduced pressure and recovered by subsequent fractionation of the vapors, in part as light distillate and in part as reilux condensate Which is returned to further conversion.

It is also within the scope of the invention to operate the process for the production of liquid residuey which is preferably recovered from the vaporizing and separating chamber to which the charging stock is supplied. When this method of operation is employed it is preferably accom,- plished simultaneous with the production of coke and the material subjected to coking may be a portion or all of the liquid conversion products from said first mentioned separating chamber or a regulated portion of the: residual liquid from the vaporizing and separating chamber to which the charging stock is supplied, or both.

One of the advantages of the invention resides in the elimination of all large high pressure Vessels, such as the high pressure reaction chambers commonly employed in most of the modern cracking plants, without sacricing the high yields or quality of light distillate products characteristic of such modern cracking installations. This advantage Will be readily apparent Without further discussion and is accomplished by substitutirrg a relatively small separating chamber 'and a succeeding vapor heating coil for the reaction chamber. Although this separating chamber may be operated at any desired pressure up to substantially the same as that employed at the outlet from the preceding heating coil, it differs materially from the usual high pressure reaction chamber with respect to size, since in the present invention it is unnecessary and undesirable to provide suicient space in this zone to allow any substantial conversion time for either the vaporous or the liquid "conversion products supplied thereto. This Zone need only be of sufficient size to permit rapid and relatively rough separation of the vaporous and liquid conversion products supplied thereto, and it is preferably operated at a suicient superatmospheric pressure to avoid any excessive entrainment of relatively high boiling liquids in the vapor stream supplied to the subsequent heating coil.

The heating coil to` which the vaporous products from the separating chamber are supplied may utilize cracking conditions varying over a relatively wide range, depending primarily upon the characteristics of the charging stock and the desired results. When it is desired to produce a motor fuel of exceptionally good antiknock quality, or when the nature of the charging stock is such that good quality motor iuel cannot be obtained except under severe cracking conditions, this heating coil may employ temperatures appreciably higher than those employed in the first cracking coil, ranging for example from 959 to ll F., or thereabouts. On; the otherv hand, when high yields of motor fuel arel more desirable than high antiknook value, or when the nature of the charging stock is such that good quality motor fuel may be produced under relatively mild cracking conditions or under temperature and pressure conditions similar to those employed in the first cracking coil, the heating coil to which the vaporous products from the separating chamber are supplied may be operated as a soaking Zone rather than a Zone of extensive more severe cracking, in which case it is preferably operated under substantially the same temperature and pressure conditions as those employed at the outlet from the rst cracking coil, although they may of course be varied somewhat to suit requirements.

The invention permits the use of any desired type of charging stock, ranging from relatively light distillates such as naphtha, kerosene, kerosene distillate, light gas oil, or the like, to heavy residual oils, and specically including the various types of crudes. Introduction of the charging stock into the vaporizing and separating chamber succeeding the coking Zone not only serves to effect vaporization of the charging stock and its separation, when desired, into low boiling and high boiling fractions, but also serves the useful purpose of scrubbing and cooling the Vaporous products from the coking chamber sufliciently to remove therefrom, prior to their fractionation for the formation of reflux condensate, entrained heavy liquids or other high boiling components of a high coke-forming nature unsuitable for return to the cracking coil for further cracking with the reflux condensate.

The accompanying diagrammatic drawing illustrates one specific form of apparatus in which the invention may be accomplished.

Referring to the drawing, heating coil I is located within furnace 2, and the oil supplied to this zone from within the system, in the manner to be later more fully described, is subjected therein to the desired temperature, preferably at a substantial superatmospheric pressure, and the heated products are discharged through line 3 and valve 4 into separating chamber 5.

Chamber 5 may be operated at any desired pressure ranging from substantially the same as that employed at the outlet from heating coil I down to substantially atmospheric pressure, al-

lthough a superatmospheric pressure of from 50 to 100 lbs., or thereabouts, per square inch, or at least sufficient to prevent excessive vaporization of the liquid conversion products supplied to this Zone and prevent the entrainment of any appreciable quantity of detrimental high boiling liquids in the vapors withdrawn from the separating chamber, is preferably employed in this zone. Chamber 5 is of suflicient size to permit fairly complete separation of vaporous and liquid conversion products in this Zone but is not sufliciently large to permit any extensive further cracking of either the vaporous or liquid products in this zone.

The liquid conversion products are withdrawn, either alone or together with a minor portion of the vapors, from the lower portion of chamber 5 through line 6 and valve 'I, and may be directed, all or in part, through line 8 and valve 9 into coking chamber ID entering this zone at any desired point or plurality of points, although only one point of introduction is shown in the drawing, or a regulated portion or all of the products withdrawn from the lower portion of chamber 5 may be directed through valve II in line 6 to vaporizing and separating chamber I2.

The vaporous conversion products separated from the higher boiling liquid products in chamber 5 are withdrawn from the upper portion of this Zone and are directed through line I3 and valve I4 to heating coil I5, wherein they are subjected to the desired degree of continued cracking by means of heat supplied from a furnace I6 of any suitable form. The heated products are discharged from heating coil I5 through line I'I and valve I8 into coking chamber I0, wherein they preferably come into direct and intimate contact with the residual liquids undergoing coking in this zone, serving to assist their reduction to coke.

Coking chamber IG is preferably operated at substantially atmospheric or relatively low superatmospheric pressure, although when relatively high pressure is employed in heating coil I5 the coking chamber may be operated at a relatively high pressure, when desired. The coke formed in chamber Ill may be allowed to accumulate therein, to be removed, by any well known means not illustrated, after the operation of the chamber is completed. Chamber I0 is provided with suitable drain line I9, controlled by valve 20. Vaporous products are withdrawn from the upper portion of the coking chamber and are directed through line 2l and valve 22 into vaporizing and separating chamber I2.

Simultaneous with the operation above described, hydrocarbon oil charging stock of the process, which, as previously mentioned, may comprise any desired type of oil, is supplied through line 23 and valve 24 to pump 25, by means of which it is fed through line 26 and Valve 21 into vaporizing and separating chamber I2. It will be understood, of course, that the charging stock may, when desired, be preheated, in any well known manner not illustrated, to any desired temperature below that at which appreciable cracking thereof will occur, prior to its introduction into chamber I2. The charging stock is contacted in chamber I2 with the hot vaporous conversion products from the coking zone and is thereby subjected to substantial vaporization, serving at the same time as a means of partially cooling and scrubbing the vaporous products from the coking zone in order to remove therefrom entrained heavy liquids or other undesirable high boiling components of a high coke-forming nature. Chamber I2 is preferably operated at a relatively low superatmospheric or at substantially atmospheric pressure in order to assist vaporization of the charging stock in this zone, and in order to assist further vaporizaticn of the liquid conversion products from chamber 5, when such material is supplied to this Zone. The high boiling residual liquids remaining unvaporized in chamber I2 are withdrawn therefrom through line 28 and may be directed, all or in part, through valve 29 to pump 30, by means of which they are supplied through line 3|, Valve 32 and line 8 to coking chamber I0, for further treatment and reduction to coke. A regulated portion or all of the residual liquid from chamber I2 may, when desired, be withdrawn from line 28 through line 5I and Valve 52 to cooling and storage or elsewhere, as desired. 'Ihe vaporous products supplied to chamber I 2 from the coking zone which remain uncondensed in this zone, as well as the vaporized components of the charging stock and the vapors evolved from any liquid conversion products from chamber 5 which are supplied to chamber I 2, are removed from the upper portion of this zone and directed through line 33 and valve 34 to fractionation in fractionator 35.

'I'he components of the vapors supplied to fractionator 35 boiling above the range of the ydesired inal light distillate product of the process' yare condensed in this Zone as reflux condensate, which is withdrawn from the lower portion of the fractionator through line 36 and Valve 31 to pump 38, by means of which it is directed through line 39 and valve 40 to further cracking in heating coil I, in the manner previously clescribed.

Fractionated vapors of the desired end boiling point, preferably comprising materials within the boiling range of motor fuel and of good antiknock value, are withdrawn from the upper portion of fractionator 35 and directed through line 4I and valve 42 to condensation and cooling in condenser 43. The resulting distillate and gas passes` through line 44 and valve 45 to collection and separation in receiver 40. Uncondensable gas may be released from the receiver through line 4'I and valve 48. Distillate may be withdrawn from receiver 46 through line 49 and Valve 5U, to storage or to any desired further treatment.

In a process of the character illustrated and above described, the preferred range of operating conditions may be approximately as follows: The cracking temperature employed at the outlet from the first heating coil may range, for example, from 800 to 950 F., or thereabouts, preferably with a superatmospheric pressure at this point in the system of from 100 to 800 lbs., or thereabouts, per square inch. The succeeding separating chamber may be operated at any desired pressure, ranging from substantially the same as that employed at the outlet from the preceding heating coil down to substantially atmospheric pressure, although a superatmospheric pressure of from 50 to 100 lbs., or more, per square inch is preferred in this zone. The second cracking coil to which vaporous products from the separating chamber are supplied may utilize any desired cracking temperature within the range of 900 to l100 F., Ior thereabouts, and the pressure employed in this. zone may range from substantially the same as that employed in the preceding separating chamber, down to substantially atmospheric pressure. rIhe coking zone may be operated at any desired pressure from substantially atmospheric up to approximately the same pressure as that employed at the outlet from the communicating heating coil and this pressure may be either substantially equalized or somewhat reduced in the succeeding vaporizing and separating, fractionating, condensing and collecting equipment; the Vaporizated at a relatively low pressure, rangi-ng from 60 lbs., or thereabouts, per square inch down to invention as it may be accomplished in apparatus such vas illustrated and above described, the charging stock, which comprises a topped crude of about 32 A. P. I. gravity, is supplied to the vaporizing and separating chamber succeeding the coking zone, wherein all but its heavy high coke-forming components are vaporized and supplied, together with the clean vaporous products from the coking Zone, to the fractionating stage of the system. Reflux condensate from the fractionator is supplied to the first heating coil, wherein it is subjected to a co-nversion temperature of approximately 950 F. at -a superatmospheric pressure of about 500 lbs. per square inch. The succeeding separating chamber is operated at substantially the same pressure, and the vaporous products from this zone are passed at substantially the same pressure through a Separate heating coil, wherein they are maintained at a substantially uniform temperature of approximately 970 F., for a predetermined time. The vaporous products from said separate heating coil are introduced into the coking chamber to' which high boiling liquid products from the vaporizing and separating chamber to which the charging stock is supplied are also directed. The coking chamber is operated at a superatmospheric pressure of approximately 45 lbs. per square inch, which is substantially equalized in the succeeding vaporizing and separating chamber as well as in the fractionating, condensing and collecting portions of the system. This operation will produce, per barrel of charging stock. approximately 65 per cent of motor fuel having an octane number of approximately 70 and about lbs. of low volatile coke of uniform quality and good structural strength, the remainder being chargeable principally to uncondensable gas.

I claim as my invention:

l. A process for the cracking of hydrocarbon oils which comprises, introducing hydrocarbon oil charging stock of relatively wide boiling range into a vap-orizing and separating chamber and therein separating its relatively low boiling components from its relatively heavy components of high coke-forming characteristics, withdrawing hot high boiling liquids` from said vaporizing and separating chamber and directly introducing the same, without intermediate cracking thereof, into a coking zone, reducing the same therein to coke by contact with hot cracked vapors, subjecting the vapors from the Vaporizing and separating -chamber to fractionation whereby their components boiling above the range of th-e desired final light distillate product of the process are condensed asreflux condensate, subjecting fractionated vapors. of the desired end boiling point to condensation, recovering the resulting distillate, subjecting reflux condensate formed by said fractionation to conversion conditions of cracking temperature and superatmospheric pressure in a heating coil, introducing'the heated oil into another separating chamber wherein separation of vaporous and liquid conversion products is accomplished without any substantial further cracking of either, withdrawing liquid conversion products from the last-mentioned separating chamber and introducing the same in regulated quantities into the same vaporizing and separating chamber to which the charging stock ing and separating zone preferably being oper-vv is supplied, wherein they are subjected to further vaporization, separately withdrawing only relatively clean vaporous products from said other separating chamber, subjecting the same to con- ;trolled conditions of further conversion under oil for the process to a separating Zone andk therein separating vapors from unvaporized oil, transferring the latter directly7 and without intermediate cracking thereof to a coking zone, subjecting the first-named vapors to continued cracking and then introducing the same into contact with said unvaporized 4oil in the coking zone, removing vapors from the coking Zone and introducing the same t0 said separating Zone for contact with the charging oil therein, fractionating the vapors from the separating Zone to condense heavier fractions thereof and supplying such condensed heavier fractions to the heating coil as said reflux condensate, and finally condensing the fractionated vapors.

CHARLES H. ANGELL. 

